Transition metal nitride

Metal nitrides are transition metal materials (titanium, vanadium, and molybdenum) that are receiving attention for pseudocapacitive study because they exhibit high electronic conductivities compared to transition oxides. Liu et al. [94] studied molybdenum nitride (Mo N) and showed that 

CV profiles for MoxN film electrode deposited at different temperatures. Source Liu, T. C. 1998. Journal of the Electrochemical Society, 145,1882. With permission.) 

Vanadium nitride has high electrical conductivity (1.67 xlO S.mi) compared to the limiting conductivity of vanadium oxide powders (V20s-nH20, 1 X 10 S.m ) [95]. Unlike titanium nitride, which does not exhibit any oxygen functionalities, vanadium nitride was confirmed by FTIR spectroscopy to have an oxygen monolayer (V2O5 0.5 nm) on the surface of the spherical nitride crystal (400°C sample 6.33 nm crystal size, 38 m. gr BET area). The 

Specific capacitance for TiN nanocrystals synthesized at different deposition temperatures and tested at varying scan rates in 1 M KOH. (Source Choi, D. and P. N. Kumta. 2006. Journal of 

Maximum capacitance of over 1300 F.gr is observed at low scan rates, and at higher scan rates of 100 mV.sec performance still exhibits 550 F.g . This is much better than other reported values (350 F.gr at 5 mV.sec ) for vanadium oxide [95]. High scan rates of 2 V.sec for the vanadium nitride electrode still yield 190 F.g indicating that vanadium nitride is capable of high power density. Stability issues due to dissolution of the oxide layer caused a large decrease in original capacitance after 1000 cycles. However, by controlling the pH of the electrolyte, stable capacitance of 400 F.g- was observed for over 1000 cycles on the vanadium nitride electrodes [95]. 

In general, the nitrides of the early transition metals are either highly conducting (e.g., TiN) or superconducting, e.g., NbN. However, the nitrides of zirconium, hafnium, and tantalum, with the metals in their highest oxidation state, are transparent insulators. 

The transamination route employed for the CVD growth of Si3N4 (Sect. 5.5.1) and AIN (Sect. 5.5.2) are also applicable for ZriN4 [202], Hf3N4, andTa3Ns [203], As with aluminum nitride, deposition occurs at temperatures significantly lower than those reported for traditional CVD routes. In each case the homoleptic amido compounds (25 and 26) were employed as the precursors. 

Crystalline films of Ta3Ns were grown above 500°C from the single source precursor [TaCl2(N-T3u)(NH- Bu)(NH2- Bu)]2 (27). However, no data on the insulating properties or film purity was reported [205]. 

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Wallace C H 1998 The rapid solid-state synthesis of group III and transition metal nitrides at ambient and high pressures PhD Dissertation University of California, Los Angeles... 

The conversion of coordinated NSCI into a nitrido ligand provides a useful synthesis of transition-metal nitrides. For example, treatment of ReCl4(NSCl)(POCl3) with triphenylphosphine generates the nitrido complex ReNClaCPPhsla. "... 

Figure 4.31 Optimized structures of transition-metal nitrides and imides (4.65).

Transition-metal nitrides, 17 218 Transition-metal oxides, 5 598... 

Source Refs. 31 and 32. Reprinted from J Cryst Growth. 66. S Iwama el al.. Growth of ultrafine particles of transition metal nitrides, pp 189-194. Copyright 1984, with permission from Elsevier Science. 

Extensive studies describe the development of new materials, such as transition-metal nitrides and oxynitrides, as new potential catalysts for hydroprocessing operations. Studies were performed to acquire information on the effect of high levels of ZSM-5 additive on light olefins and gasoline composition in FCC.289 It was found that ZSM-5 can substantially increase propylene and butenes, and... 

For quenching experiments, which were necessary to freeze-in the equilibrium states between the phase bands, the samples were reheated in a vacuum furnace under 500 mbar N2 to the original annealing temperature and dropped onto a copper plate kept below 470 K (200°C). With this treatment the Group 5 transition metal nitrides underwent a slight change in surface composition because it was impossible to adjust the appropriate nitrogen pressures. This, however, did not influence the compositions at the interface boundaries inside the diffusion couples. 

Figure 8.8 Structure of FeWN2. An example of a ternary transition metal nitride containing octahedral iron and trigonal prismatic tungsten. Small white = Iron, Black = Tungsten, Large...

This paper consists of three parts. The first part describes the high pressure synthesis of bimetallic compounds of NbN and MN where M is a Group 13 metal such as Al, Ga, or In. The second part discusses crystal structure investigations of a series of alkaline earth and transition metal nitrides, carried out to understand the bonding surrounding the transition metals. The third part describes the preparation of new metastable transition metal nitride and their solid solutions by rf-sputter deposition. 

Recently, studies from outside the Soviet Union have started to appear in the literature. In the US, Holt and Kingman17 reported the synthesis of transition metal nitrides not from gas-solid combustion reactions, but by using sodium azide as a solid source of nitrogen, according to the scheme ... 

Transition metal nitrides and carbides can be described, generally speaking, as insertion compounds of nitrogen or carbon in the metal network.1 In fact, strong metal-nonmetal interactions exist which induce structural modifications.1,2 These compounds form a class of materials with unique physical3,4 and catalytic1,5,6 properties. The term platinoids has been used to illustrate their potential in reactions traditionally catalysed by noble metals. 

The first syntheses of transition metal nitrides and carbides were derived from metallurgical processes,1,3 and consisted in the nitridation or carburization of the metal or of the oxide at severe conditions, in particular at high temperatures (>1500 K). Consequently, the resulting powders generally had low specific surface areas (Sg). 

Combustion synthesis of transition metal nitrides an overview 233... 

The synthesis of ternary transition metal nitrides through the reaction of two binary nitrides (Table 8.1, Reaction 1) or by nitriding two metals (Table 8.1, Reaction 2) has been relatively unsuccessful. Consequently, until recently, there was little or no information concerning the synthesis and structures of these phases. Lately, several transition metal ternary nitrides have been made through other synthetic routes, such as metathesis reactions and ammonolysis. For example, the ternary nitride CuTaN217... 

Figure 8.9 Structure of MnMoN2 and j3-MnWN2. Examples of ternary transition metal nitrides containing octahedral manganese and trigonal prismatic molybenum/tungsten. Small white = Manganese, Black = Molybenum/Tungsten, Large white = Nitrogen.

The synthesis of transition metal nitrides by SHS was first mentioned by Merzhanov and Borovinskaya.6 The authors reported the crystal structure... 

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